The invention relates to a press switch for controlling at least two functions in response to respective pressures exerted on the switch.
Such a switch is used for various types of electrical equipment, such as cameras, video cameras, or telephones, for example. The purpose of such a switch is specifically to minimize the number of keys in such equipment, or to make it more ergonomic.
With this type of switch, a first press at lower pressure actuates a first function, for example a preparatory mode such as preselection. Thereafter, a second press at higher pressure serves to actuate a second function, for example an operating mode such as validating the preselection.
Document U.S. Pat. No. 5,313,027 discloses a switch of the above type comprising an insulating substrate having an outer annular contact zone and an inner annular contact zone. A deformable conductive cup disposed in register with said zones is adapted to be in contact firstly with the outer zone on being subjected to a first pressure and secondly with both zones on being subjected to a greater pressure. The cup is covered in an insulating membrane which is fixed to the substrate by means of spacers so as to hold the cup away from the zones in a rest position.
That switch suffers from various drawbacks. Not only are additional pieces necessary for keeping the cup out of contact with the substrate, but it is also difficult to master the amount of space that is required between the cup and the substrate in such a situation. The edges of the cup must lie in a plane that is parallel to the substrate so that the contact due to the first pressure is complete contact.
Furthermore, the fixing of the cup to the membrane is complex and must be perfectly done for proper operation.
There also exist switches comprising a pair of cups disposed one above the other so that on a first pressure, the outer cup urges the inner cup into contact with the outer zone of the substrate, and a second pressure causes the inner cup also to come into contact with the inside zone.
Such a solution is difficult to implement and does not make for a switch that is compact, in particular because of the presence of the two cups.
An object of the invention is thus to mitigate the drawbacks of the prior art by proposing a switch that provides high performance, that is simple to implement, and that is compact, the switch being capable of being used in ergonomic manner to give access to different functions.
To this end, the invention proposes a press switch of the above-specified type, comprising an insulating substrate with at least first and second conductive zones suitable for triggering first and second functions, respectively. At least the first conductive zone has at least two portions that are electrically insulated from each other, a first portion being connected to an inlet track and a second portion to an outlet track. The second conductive zone is also connected to at least one additional outlet track.
The switch also comprises a spring having at least first and second contact zones suitable for coming into contact respectively with the first and second conductive zones as a function of the amount of pressure exerted on the spring. The first contact zone has at least two regions that are electrically interconnected and suitable respectively for coming into contact with the portions so as to interconnect the inlet and outlet tracks.
The spring can take up at least three positions:
a rest position in which it is in contact with part of at least the first conductive zone, the inlet track being connected to none of the outlet tracks and no function being performed;
a first actuated position in which a first amount of pressure causes a connection to be established between the inlet track and the outlet tracks of the first conductive zone, said first actuated position being for triggering performance of the first function; and
a second actuated position in which a second amount of pressure, greater than the first, causes contact to be established between each contact zone with the corresponding conductive zone, said second actuated position being for triggering performance of the second function.
The invention also provides electrical equipment including an above-mentioned press switch, and means for performing at least a first function and a second function, with performance of the functions being triggered in response to respective pressures exerted on the switch.
The function triggered in the first actuated position is, for example, a preselection function, while the function triggered in the second actuated position is, for example a selection function.
In a particular embodiment, the insulating substrate has two conductive zones each occupying a substantially circular ring, the first conductive zone lying outside the second conductive zone.
In a first embodiment, the first conductive zone has at least three portions including a first portion connected to an inlet track and second and third portions connected via outlet tracks to circuits that are programmed so that the first function can be triggered as soon as all three portions have come into contact with the corresponding regions.
In a second embodiment, the first conductive zone has at least three portions, of which a first portion is connected to an inlet track and the second and third portions are connected via outlet tracks to circuits programmed so that a first action can be triggered when the first and second portions are brought into contact, while a second action can be triggered when the first and third portions are brought into contact.
In this situation, the electrical equipment can have means for preforming at least two actions enabling a cursor to be moved in two different directions, in response to actuation of the switch.
The switch can then form part of a navigation button.
At least a portion of the outside face of the spring adheres to a flexible holding membrane adjacent to the insulating substrate outside the conductive zones. This membrane holds the spring in the rest position while enabling it to move to occupy the first and second actuated positions.
The switch of the invention also comprises a key suitable for acting on the outside face of the spring so as to exert the pressures thereon.